Liquid detecting device



Feb. 13, 1940.

H. E. JORDAN LIQUID DETECTING DEVICE Filed Feb. 11, 1939 Patented Feb. 13, 1940 UNITED srAT Es [PATEN emu-1' JJQUID DETECTING .navron Henry Ewin Jordan, Los Angela; Calif. Application February 11. 1939, Serial No. 255,396

' a m. i (61., 116-118) This invention relates broadly to liquid detecting' devices, and is particularly useful in apparatus for determining whether or not liquid is present in a predetermined location, although the invention may be employed in gauges for determining what the levelv of liquid is with respect to a reference standard.

A general object of the invention is to provide a liquid detecting device that is simple,,reliable,

has no moving parts, and may be installed in containers, tanks, pipes, and the like, without danger of causing leakage or introducing afflre hazard in the case of imflammable liquids or u gases.

I accomplish the foregoing objects in accordance with the present invention by utilizing a rod of transparent material which is exposed at a point intermediate its ends to the medium tobe investigated, in combination with means for transmitting light longitudinally through the rod and determining variations in the amount of light transmitted from one end of the rod to the other.

It is well known that a rod of transparent material having an index of refraction of substantial magnitude will ordinarily transmit a substantial amount of light from one end to the other, even though the rod may be bent. The reason for this is that lightseeking to escape through the lateral surface of the rod is totally reflected back so into the rod unless the angle of incidence of the light at the surface of the rod is relatively small.

' (The angle of incidence being the angle between the ray of light and a line drawn normal to the reflecting surface at the point of incidence.) The angle of incidence above which all light is totally reflected, is known as the critical angle and varies with the index of refraction of the material. For ordinary glass, it is in the neighborhood of 40. Therefore when a rod of glass is positioned in air or other gas and light is directed into one end of therod, most of the light entering the rod will follow it to the oppositev end and there emerge because most of the light 'will enter the rod at an angle less than to the lateral surface of the rod, and will be totally re- ,lflected at a low angle from different points on the lateral surface of the rod until it reaches the opposite end. 'However, if a portion of the so rod intermediate the end is immersed in a liquid having an index of refraction of the same order of magnitude as the rod material, then the rod substantially completely loses its internal reflectlng properties, permitting much of the light to greatly reducing the total amount of light transmitted to the remote and of the-rod and substantially reducing the intensity of the transmitted light at the remote end.

I have discovered that by immersing a portion, 5 even a small portion, of the lateral surface of .such a rod in liquid, the diminution in the intensity of illumination of the remote end of the tube is readily observable.

transmission of light by internal reflection through a transparent rod surrounded by air;

Fig. 4 is a schematic diagragl illustrating the loss of light from such a rod when immersed in 25 liquid;

Fig.6 is a sectional view showing a gauge in accordance with the invention, installed on a gasoline tank for indicating when the tank is full; and so i Fig. 6 is a plan view of the outer portion of the spout and related apparatus of Fig. 5.

The gauge disclosed in Fig. 1 comprises a relatively elongated rod I of transparent material having a reverse bend 2 substantially at the middle thereof and mounted in a metal frame 3 for safety. The frame 3 consists of two tubular members 4 and 5, respectively, which enclose the greater portion of the straight lengths of the rod I. The speciflc construction is better dis- 0 closed in Fig. 2, showing a gauge identical in all respects with that shown in Fig. 1, except that the rodisformed in a plurality of pieces instead of onepiece. The corresponding parts of Fig. 2 bear the same reference numerals as Fig. 1 with the suflix a. As has been indicated, the device shown in Fig. 2 has the rod la formed in four. sections with a short gap-intermediate the sec-, tions. There is no advantage. from the standpoint of efficiency of operation, in having the 50 gap 6, but it may have advantages in manufacture and is disclosed as a'possible variation of the structure shown in Fig. 1 for that reason. As shown in .both Figs. 1 and 2, one end of the rod I or la projects beyond the end of the enclosing 5| 2 protecting tube 8 so that it is exposed to light.

The other end of the rod in terminates within' the end of its enclosing tube 4 and the latter is flared out, funnel shape, at the upper end, and is preferably coated on its inside surface with dark paint to in part protect the adjacent end of the rod from external illumination. Forconvenience the exposed end of the tube may be identified with the reference numeral 1 and the protected end by the reference numeral 8.

One or both ofthe enclosing tubes 4 and- I may bear gradations 8, indicating the distance from the lower end of the device. The gauge described with reference to Figs. 1 and 2 is intended to be lowered into a tank or receptacle I is very markedly decreased, indicatingto the.

operator that the lower end of the gauge has contacted the liquid. By then observing the gradations 8 with reference to the top of the tank or any other desired reference standard, the position of the liquid level is ascertained.

To check the results, the operator may lift the gauge slightly to carry the rod clear of the liquid;

thisimmediately results in increase of the'intensity of the illumination of the end 8 to its former value despite the fact that more or less of the liquid may adhere to the surface of the rod.

The operation described may be carried on without any special illumination other than what may be present. from daylight or the usual artificial illumination. Of course, if desired, a more intense illumination of the end 8 with a correspondingly more marked decrease of such 11111-7 minationwhen the lower end of the rod is immersed in the liquid, may be obtained by holding a lamp closely adjacent the end lot the rod. It is withinv the scope of the invention to, provide, if desired, a special lamp, such as a small electric bulb, immediately above the end 1 of the rod to produce an intense local illumination.

The theory of operation of the gauge as described, may be readily understood from reference to Figs. 3 and 4, which show what happens to a random ray of light transmitted down through the rod from the end 1. It will be observed that in Fig. 3, showing the case in which the rod is not immersed in liquid, the ray of light I! travels obliquely at 'a low angle from one lateral wall .of the rod to the other, being completely reflected at each point of contact by virtue of the diiference in the refractive powers of the rod material and oi. the air surrounding it. In Fig. 4, however, the ray l2, after contacting the lateral wall in three places and being totally reflected each time, next reaches the outer surface of the rod at a point where the latter is in contact with liquid 13, it being assumed, in this particular instance, that the liquid l8 has thesame refractive index as the material of the rod, under which conditions the Of course ordinarilythe liquid testedwould not have exactly the sameindex of refraction as/the rodmateri'al and there would usually be parent some refraction of the ray I2 at the point of emergence from therod- Furthermore, if the rod material has a much greater index of refraction than the liquid, then rays of light striking the liquid-rod contact surface at a very low angle, might still be internally reflected back into the rod. However, even with a substantial discrepancy between the indexes of refraction of the rod and the liquid, respectively, there will be a substantial diminution in the total number 1 of rays totally reflected, with corresponding reduction in intensity of illumination at the end 8 A particularly useful form ofthe invention is disclosed in Figs. 5 and 6 in which a gauge in accordance withthe invention is mounted in the filler spout 15 of the gasoline tank l6 of an automobile. As is well known, most modern automobiles have fuel tanks mounted well within the sheet metal body of the automobile, necessitating relatively long filler pipes leading to the exterior of the body. Furthermore these filler pipes or spouts are often curved or bent. As a result, it is impossible for a service station attendant filllng the tank to see into the tank and determine ,by direct observation when it is full.

Therefore, if the operator desires the tank filledexactly full. Even if such gauges were sufliciently reliable, they are usually out of sight of the attendant, who is filling the tank, and it is highly desirable to have an accurate and reliable gauge positioned adjacent the filler spout to indicate to the attendant exactly when the tank is filled.

As shown in Figs. 5 and 6, a gauge ll of the general type described inconnection with Figs. 1 and 2, is incorporated in the spout It with its lower and positioned at the juncture of the spout with the tank. As shown in Fig. 5, the rods and tubes of the gauge I! are bent to conform to the curvature of the filler spout It so that they will lie close along the side thereof and not interfere with the insertion of a gasoline nozzle into the spout. Various methods may be employed for anchoring the gauge in position.

I have shown in Fig. 5 an attachment that may be secured to existing tank spouts l5. Thus I 'have provided an extension nipple I8 having with apertures in its side wall through which the tubes of the gauge II project to the exterior. To anchor the tubes of the gauge to the nipple, the/tubes may be threaded to receive nuts 28 and 2| on the interior and exterior sides of the nipple, respectively. Furthermore, the funnel or light shield 22 may also be threaded onto the tube associated with the end -8 of the lightconducting rod, and suitable washers 28 may be provided to make a fluid-tight connection.

The operation of the gauge shown in Figs. 5 and 6-will be obvious. The service station attendant simply observes the end 8 of the transrod while he is filling the tank, and is immediately informed when the liquid level rises to the top 01 the tank by the dimming oi the end 8 of the rod.

The transparent rod employed in my invention may be made of many different materials, in-

cluding various types of glass, quartz,-and-some of the newer plastic materials, an example of which is sold under the trade name of Leucite".-

It is desirable that the material have a high 10 index of refraction, although there is no particular lower limit for this value. In general, the higher the index of refraction, the sharper the rod may be bent without losing light at the bend in air.

Althoughin the particular device shown in the drawing the portion of the rod that is to be immersed in the liquid is bent, this is not essential, although it is desirable. The eiiect described is apparent even though the liquid contacts a go straight portion of the rod because most of the light transmitted through the rod consists or rays extending at random in various directions at small angles to the longitudinal axis of the rod (as shown in Fig. 4), and any rays impingin I upon the surface where it is immersed in liquid will pass out of the rod unless the angle of incidence is very large and the index of retraction of the liquid is a great dealless'than that of the rod material.

80 Although for purposes of explaining the invention certain relatively .simple embodiments thereof have been described in detail,'it will be' understood by those skilled in the art that the invention is applicable to much more compli- 85 cated apparatus, as, for instance, gauges in which.

material having two end portions exterior of said receptacle and having an intermediate portion within saidreceptacle, one of said end portions being exposed to light, which light is conducted along said rod to illuminate the other end to an 0 extent varying with the. light-conducting emciency of said rod, at least a portion of said rod within said receptacle having its suriace directly exposed to thereceptacle contents whereby its internal reflection characteristics and hence its,

. light-conducting efliciency, ,varies accbrding .to the refractive oi the tank contents.

2.'lhecombinationasdescribedinclaimi,in

- ceive a filler cap.

which said receptacle comprises a tank having an elongated filler neck with said rod extending through said filler neck substantially to the juncture of the neckand tank.

T3. The combination as described in claim 1, in 5 which said receptacle comprises a'tank having an elongated curved filler neck with said rod extending through and curved to conform with said filler neck.

4. The combination as described in claim 1, in 10 whichsaid receptacle has a filler opening and the two end portions of said rod are positioned closely adjacent each other and adjacent said filler opening.

5. The combination as described in claim 1, in 5 which said rod is discontinuous, consisting of sections, with each pair of adjacent sections having substantially parallel abutting faces through which light is transmitted through one'section to the next.

6. A device for indicating the presence or absence .of liquid, comprising an elongated lightconductive rod of transparent material having one end adapted to collect light for transmission longitudinally toward the otherend, the other Q5 having elongated filler necks, said attachment comprising a fitting attachable to the end of said filler neck with a light-conductive rod anchored to said fitting, said rod being doubled back on itself and the two ends exposed to view ad- 40 jacentsaid flttinfifllhe intermediate portion of said rod being adapted to extend through said flller neck substantially to the junctur'e of the filler neck and tank, whereby rise of liquid in the tank to the filler neck thereof varies the lighttransmission characteristics of said rod and the degree of illumination of at least one end or said rod. v

8. An attachment as described in claim 'Lin which said fitting comprisesan. extension neck attachable to the end of said filler neck, with the two ends of said rod extended through the wall or said extension neck to the exterior thereof, the

end of saidextension neck being adapted to re- HENRY EWIN JORDAN. 

